The use of wigs and hairpieces are primarily for bald people or to supplement thinning hair. At the present there are no compositions which can create the appearance of hair on a person having bald patches.
To attempt to hide bald or balding areas on scalps, there have been some formulations which are paint-like that coat the scalp the same color as the user's hair. In this way, the contrast between the darker hair and the lighter scalp is reduced giving the appearance of fuller hair. These paints also adhere to the existing strands of hair remaining on the scalp giving the appearance of thicker hair. However, as a viewer gets closer to the user's scalp, the viewer can visibly discern that the user's scalp is coated with a non-natural powdery substance.
Other types of hair fillers are expensive and are not readily available for instant use.